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Virus production and viral antigen expression in porcine blood monocytes inoculated with pseudorabies virus
1Laboratory of Veterinary Virology, Faculty of Veterinary Medicine, University of Gent, Belgium.
Abstract:
Interactions of pseudorabies virus (PRV) with peripheral blood mononuclear cells (PBMC) were studied. T-lymphocytes, B-lymphocytes and monocytes were selected or depleted from the PBMC fraction by means of several separation techniques. After inoculation with virulent PRV in vitro, the percentage of cells that expressed viral antigens was determined in the different subpopulations by immunofluorescence. The susceptibility of monocytes depended on the method of isolation. When plasma-coated polystyrene culture grade dishes were used, 17 to 26% of the monocytes showed expression of viral antigens. However, PRV antigens were detected in only 2% of the monocytes when the cells had first been labelled with monoclonal antibodies against a monocyte marker and subsequently separated on polystyrene bacteriological Petri disches coated with anti-mouse monoclonal antibodies. In subpopulations of unstimulated T- and B-lymphocytes only 0.4 to 0.7% of the cells were found positive by immunofluorescence. Viral antigens appeared in the cytoplasm and on the cell membrane of monocytes isolated on plasma-coated dishes starting 5 h after inoculation and the expression was found in a maximal number of monocytes, 7 to 8 h after inoculation. The intracellular and extracellular virus progeny titers obtained in monocyte cultures were low, ranging from 10(4.3) to 10(5.2) TClD50 per 10(6) inoculated monocytes. The percentage of inoculated monocytes which produced infectious PRV was 0.1% in two experiments and less than 0.01% in one experiment. The results indicate that although monocytes are the most susceptible subpopulation of unstimulated PBMC to a PRV infection in vitro, replication is clearly restricted. Only a subset of monocytes expresses viral antigens and an even smaller fraction produces infectious virus.
Insights
Pseudorabies virus (PRV) primarily infects monocytes within peripheral blood mononuclear cells (PBMC) in vitro. However, PRV replication in these monocytes is restricted, with only a small subset expressing viral antigens and producing infectious virus.
Area of Science:
- Virology
- Immunology
- Cell Biology
Background:
- Pseudorabies virus (PRV) is a significant pathogen affecting various animal species.
- Understanding PRV interactions with host immune cells is crucial for disease control.
- Peripheral blood mononuclear cells (PBMC) are key components of the immune system.
Purpose of the Study:
- To investigate the interaction between PRV and different subpopulations of PBMC in vitro.
- To determine the susceptibility of T-lymphocytes, B-lymphocytes, and monocytes to PRV infection.
- To characterize the replication and antigen expression of PRV within susceptible cells.
Main Methods:
- Isolation and depletion of T-lymphocytes, B-lymphocytes, and monocytes from PBMC.
- In vitro inoculation of cell subpopulations with virulent PRV.
- Immunofluorescence assay to detect viral antigen expression.
- Quantification of intracellular and extracellular virus progeny titers.
Main Results:
- Monocytes showed the highest susceptibility to PRV infection among PBMC subpopulations.
- Viral antigen expression in monocytes was dependent on the isolation method, ranging from 2% to 26%.
- T- and B-lymphocytes exhibited very low susceptibility (0.4-0.7%) to PRV infection.
- PRV replication in monocytes was restricted, with low virus progeny titers and a small percentage of infectious virus-producing cells.
Conclusions:
- Monocytes are the most susceptible PBMC subpopulation to PRV infection in vitro.
- PRV replication is significantly restricted in infected monocytes.
- Only a subset of monocytes expresses viral antigens and an even smaller fraction produces infectious virus, suggesting a limited productive infection.
